The present invention relates to a differential response light-receiving device comprising a semiconductor sensitized by a dye, and particularly to such a differential response light-receiving device that makes selective, immediate response to a moving content in an image. Further, the present invention relates to a composite light-receiving device, which comprises the differential response light-receiving device and a stationary response light-receiving device making different response to a photoimage, to receive a static photo-information and a dynamic photo-information at a two-dimensionally same surface at the same time. Furthermore, the present invention also relates to an image sensor using the differential response light-receiving device or the composite light-receiving device.
Recently, remarkable progress has been made in technology for fine manufacturing art and in the photolithography so that image information-recording density has been improved more and more.
Conventionally, development of light-receiving devices (light-sensitive devices) comprising high-sensitive sensors, high-density recording devices, etc. substantially has depended on the fine manufacturing art using a silicon substrate, thus, functions of the light-receiving devices have been controlled by the silicon and components disposed thereon. Though the image information-recording density has been improved, the image information received by the light-receiving device is inevitably processed in circuit and software. Solid light-receiving devices composed of silicon hardly have various functions required for use in an image-processing system of the next generation, for example, a function for discriminating and processing an information like an animal sight with a pattern recognition and an extraction of motion. Consequently, to use the solid light-receiving devices in a visual information-processing system, a high-performance computer plays an extremely important role for processing information outputted from the solid light-receiving device.
As a so-called, differential response light-receiving device that directly converts variations in optical input signals to an electrical signal, an electrochemical cell comprising a transparent electrode/a bacteriorhodopsin thin film/an electrolyte/counter electrode has been disclosed in Japanese Patent Laid-Open No. 3-205520, and an electrochemical cell comprising a transparent electrode/an electrolyte/a silicon substrate has been disclosed in Japanese Patent Laid-Open No. 11-37838. The former electrochemical cell is known as a first example of the differential response light-receiving device that makes time-differential response to quantity of light, however, the cell uses a protein to be poor in sensitivity and stability. Although the latter electrochemical cell is improved with respect to the sensitivity, the cell uses the silicon substrate to have disadvantages as follows: (i) the silicon substrate is formed by precisely processing Si wafer or by vapor depositing silicon, resulting in high costs; (ii) the silicon is sensitive to infrared light and heat rays so that the cell is decreased with respect to S/N ratio in the image detection under dark light sources in a room to need an infrared light cut filter. Further, both of the two electrochemical cells have a narrow range of choice with regard to spectral wavelength characteristics, thereby not being suitable for color sensors.
An object of the present invention is to provide a differential response light-receiving device that overcomes the above problems of the prior art, and a differential response image sensor that uses the device to be capable of discriminating even color information. Further object of the present invention is to provide a composite light-receiving device capable of sensing color information, a static photo-information and a dynamic photo-information at the same time, and an image sensor using the composite light-receiving device.
A differential response light-receiving device of the present invention comprises: a semiconductor electrode comprising an electrically conductive layer and a photosensitive layer containing a semiconductor sensitized by a dye; an ion-conductive electrolyte layer; and a counter electrode, and makes time-differential response to quantity of light to output a photoelectric current. In the differential response light-receiving device of the present invention, the ion-conductive electrolyte layer is preferably free of redox species. The semiconductor is preferably a metal chalcogenide, more preferably a metal oxide selected from the group consisting of TiO2, ZnO, SnO2 and WO3.
The differential response light-receiving device may comprise a plurality of semiconductor electrodes, photosensitive wavelengths of the semiconductor electrodes being different from each other, the ion-conductive electrolyte layer being disposed between the semiconductor electrodes and the counter electrode. In this case, the semiconductor electrodes are preferably arranged in such order that the photosensitive wavelengths are increasing from light incident side of the differential response light-receiving device, and the semiconductor electrodes may comprise a blue-sensitive semiconductor electrode, a green-sensitive semiconductor electrode and a red-sensitive semiconductor electrode arranged in this order from the light incident side.
A composite light-receiving device of the present invention comprises the differential response light-receiving device and a stationary response light-receiving device. The differential response light-receiving device and the stationary response light-receiving device are arranged horizontally to said light-receiving surface or the differential response light-receiving device is stacked on the stationary response light-receiving device in the direction of light incidence.
In the composite light-receiving device, the stationary response light-receiving device preferably comprises: a semiconductor electrode comprising an electrically conductive layer and a photosensitive layer containing a semiconductor sensitized by a dye; a charge transfer layer comprising a hole-transporting material or an electrolyte composition containing redox species; and a counter electrode. In the stationary response light-receiving device, the semiconductor is preferably a metal chalcogenide, more preferably a metal oxide selected from the group consisting of TiO2, ZnO, SnO2 and WO3.
The stationary response light-receiving device may comprise a plurality of semiconductor electrodes, photosensitive wavelengths of the semiconductor electrodes being different from each other, the charge transfer layer being disposed between the semiconductor electrodes and the counter electrode. In this case, the semiconductor electrodes are preferably arranged in such order that the photosensitive wavelengths are increasing from light incident side of the composite light-receiving device, and the semiconductor electrodes may comprise a blue-sensitive semiconductor electrode, a green-sensitive semiconductor electrode and a red-sensitive semiconductor electrode arranged in this order from the light incident side.
An image sensor of the present invention comprises a plurality of pixels, each of the pixels comprising the differential response light-receiving device of the present invention or the composite light-receiving device of the present invention.